The operation of an electric phaser for a cam phasing system is such that a sun gear or planet gear carrier is stationary, and a ring gear and other member rotates with a camshaft, which is driven by a crank through a gear, belt or chain system. One method of control is to use a first position sensor mounted on the crankshaft and a second position sensor mounted on the camshaft. After the cam is rotating, the angular position of the cam can be calculated by an electronic control unit (ECU) and a signal can be sent to move the stationary member to adjust the phaser angle of the cam, for example, see U.S. Pat. No. 5,680,837. Other control systems can be seen in U.S. Pat. No. 7,640,907; and U.S. Pat. No. 7,243,627.
U.S. Published Patent Application No. 2012/0053817 discloses a method for sensing the position of a camshaft in an internal combustion engine having a camshaft phaser for controllably varying the phase relationship between a crankshaft of the internal combustion engine and the camshaft, where the camshaft phaser is actuated by an electric motor and includes a gear reduction mechanism with a predetermined gear reduction ratio and rotational position means for determining the rotational position of the electric motor. The method includes generating a rotational position signal indicative of the rotational position of the electric motor by using the rotational position means to determine the rotational position of the electric motor, and calculating the position of the camshaft based on the rotational position signal and the gear reduction ratio of the gear reduction mechanism. The rotational position means includes three Hall Effect sensors, one sensor disposed between each of the three electrical windings in the stator of the motor, for generating a rotational position signal indicative of the rotational position of the rotor. The published application asserts that this method can also be used to detect the position of the rotor even at zero revolutions per minute (RPM) as long as the engine control module (ECM) is still powered on. The disclosure further asserts that using Hall Effect sensors to determine the position of the camshaft, through the mathematical equations corresponding to the attached harmonic gear drive unit, eliminates the need for a separate sensor for determining the position of the camshaft. While the disclosed configuration may be suitable for the intended purpose, the complexity of the sensor configuration increases cost of the motor and potentially raises issues regarding the simplicity of assembly and/or initialization of the assembled motor system.